textproduct: Albany

WHAT HAS CHANGED

The Storm Prediction Center has expanded the Marginal Risk (Level 1 of 5) for Severe Weather farther north to now encompass most of eastern New York and western New England.

KEY MESSAGES

1) Scattered to numerous showers and thunderstorms return for the end of the work week, bringing the potential for locally heavy rain and isolated damaging wind gusts, particularly today.

2) Increasing heat and humidity also return today into Friday, which may result in heat-related impacts, mainly in eastern Ulster, western Dutchess and southern Litchfield CT.

DISCUSSION

KEY MESSAGE 1...

Despite weak upper-level forcing, ample warmth and moisture surging into the region along the northwest periphery of a Bermuda High will be sufficient to drive surface-based forcing for ascent for the initiation of scattered to numerous showers and thunderstorms across the region today. In fact, the combination of high temperatures widely reaching the mid to upper 80s and dewpoints the low to mid 70s will see SBCAPE values reach 2000-3000 J/kg by this afternoon. This appreciable instability, paired with deep layer shear on the order of 20-35 kt and meager mid- level lapse rates (generally < 6 C/km) yield the low, though non-zero probability (~5-10% severe thunderstorms) of isolated severe- level convection this afternoon. Therefore, the Storm Prediction Center has not only maintained, but expanded, the Marginal Risk (Level 1 of 5) for Severe Weather across most of our area. The primary threat for any storm that reaches severe strength will be locally damaging wind gusts. However, should breaks in cloud cover not occur as some of the guidance suggests, it could be difficult for storms to grow tall enough to reach severe strength. Additionally, some of the latest CAMs are showing subtle low- to mid-level capping inversions which could also act to inhibit storm growth.

That said, even if developing showers/storms this afternoon don't evolve into severe-level convection, any shower or non- severe thunderstorm will be capable of producing gusty winds and moderate to heavy rainfall. The "ample moisture" mentioned previously can be classified more accurately as above-normal atmospheric moisture content for this time of year given PWAT values achieve +2 STDEVs (~ 2-2.2" across our CWA). Warm and efficient precipitation processes paired with high instability will support frequent moderate to heavy downpours this afternoon. And, with fairly slow storm motion, potential for training convection, and wet antecedent conditions, isolated flash flooding cannot be ruled out. The Weather Prediction Center has therefore outlined our entire area in a Marginal Risk (Level 1 of 4) for Excessive Rainfall. Likewise, precipitation loading will promote rapid downward acceleration (DCAPE values ~500-700 J/kg) and resulting gusty winds associated with showers and thunderstorms.

Friday, though the environment will be similar, is a little more uncertain than today. HiRes guidance is highly varied, given the short lead time, regarding the coverage of another potential round of showers and thunderstorms. While some model solutions point to very limited coverage of convection, others have more robust storms than what is projected for today. The thinking behind this is that some of the guidance is erring towards more convection today, which could stabilize the environment sufficiently to inhibit convection tomorrow, while others are resolving a potential remnant MCV that tracks through the Ohio Valley and drives stronger convection here tomorrow. With another hot, humid day anticipated tomorrow with slightly more upper-level forcing given an approaching shortwave, the latter is certainly possible. In fact, the latest REFS continues to show low probabilities (~5-14%) for severe-level wind gusts for Friday. We will continue to monitor trends in the guidance to iron out the coverage details. But as of right now, the Storm Prediction Center has maintained a Marginal Risk just to our south for Friday. The Weather Prediction Center, too, has maintained a Marginal Risk for Excessive Rainfall given the persistent potential for heavy rainfall within any showers and storms that may develop.

Additional showers and thunderstorms are expected heading into the beginning of the weekend as the system partially responsible for our convection today and possibly tomorrow finally starts to shift into the region from the northwest. We will continue to have the potential for moderate to heavy downpours with gusty winds within these showers and storms so for the third day in a row, we will remain in a Marginal Risk for Excessive Rainfall.

KEY MESSAGE 2...

Today and tomorrow will be very warm and humid given our position relative to the Bermuda High to our southeast. High temperatures both days will widely reach the mid to upper 80s with dewpoints in the low to mid 70s in valley areas. That said, the most uncomfortable areas will be portions of the lower Mid- Hudson Valley (eastern Ulster and western Dutchess Counties) and southern Litchfield County where a Heat Advisory remains in effect from 11 AM today through 8 PM Friday. Here, heat index values, or feels-like temperatures, will reach up to 98 degrees Fahrenheit. Caution is advised particularly to those who are susceptible to heat-related illness.

AVIATION /12Z THURSDAY THROUGH MONDAY/

MVFR/IFR cigs will linger at KPOU and KPSF through around 14Z-16Z/Thu, with perhaps a brief period of MVFR Cigs developing at KALB between 12Z-15Z/Thu. Otherwise, mainly VFR conditions for this afternoon outside of scattered showers/thunderstorms that develop. Brief periods of MVFR/IFR Vsbys and MVFR Cigs will be possible within any heavier downpours. Showers/thunderstorms could linger through 02Z/Fri, especially at KPSF and KPOU. Thereafter, patchy ground fog/low clouds and IFR/LIFR conditions (mainly Vsbys) may develop (20-40% chance), with greatest chances at any locations which receive prior showers/thunderstorms.

Light/variable winds will become south to southwest at 5-10 KT by late morning through this afternoon, then become light/variable shortly after sunset. Winds will be stronger, and variable in direction in and near any thunderstorms.

Outlook...

Friday Night: Moderate Operational Impact. Scattered SHRA...TSRA. Saturday: High Operational Impact. Likely SHRA...TSRA. Saturday Night: Moderate Operational Impact. Chance of SHRA. Sunday: Low Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Monday: Moderate Operational Impact. Chance of SHRA...TSRA. Monday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Tuesday: Moderate Operational Impact. Chance of SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Heat Advisory from 11 AM this morning to 8 PM EDT Friday for CTZ013. NY...Heat Advisory from 11 AM this morning to 8 PM EDT Friday for NYZ064-065. MA...None. VT...None.